Comparison of six D-dimer methods in patients suspected of deep vein thrombosis

Protocols for D-Dimer Measurements for Aid to Diagnosis or Exclusion of Venous Thromboembolism

Measuring D-dimer is commonly used as a surrogate to indicate a clot-forming process, with subsequent lysis. This test has two primary intended uses: (1) as aid to diagnosis of various conditions and (2) venous thromboembolism (VTE) exclusion. If the manufacturer cites a VTE exclusion claim, the D-dimer test must only be used in evaluating patients with a non-high or unlikely pretest probability for pulmonary embolism and deep vein thrombosis. D-dimer kits with only aid to diagnosis claim should not be used for VTE exclusion. The intended use of the D-dimer may vary by region, and readership should consult manufacturer instructions for use to assure proper use of the assay. In this chapter, several methods for measuring D-dimer will be described.

Effects of altered blood flow induced by the muscle pump on thrombosis in a microfluidic venous valve model

Deep vein thrombosis (DVT) often occurs in the lower limb veins of bedridden patients and greatly reduces the quality of life. The altered blood flow in venous valves induced by the insufficient efficacy of the muscle pump is commonly considered as a main factor. However, it is still a great challenge to observe the altered blood flow in real time, and its role in the formation of thrombi is poorly understood. Here we make a microfluidic venous valve model with flexible leaflets in a deformable channel that can mimic the motion of valves and the compression of vessels by muscle contraction, and identify the stasis and intermittent reflux in the valve pocket generated by the muscle pump. A thrombus forms in the stasis flow, while the intermittent reflux removes the fibrin and inhibits the growth of the thrombus. A flexible microfluidic device that can mimic the motion of valves and the contraction of vessels would have wide applications in the research on cardiovascular diseases.

Diagnostic approach to deep venous thrombosis and pulmonary embolism in the critical care setting

Considerable progress has been made during the last 30 years in the prevention, diagnosis, and therapy of venous thromboembolism. This article discusses the epidemiology, pathophysiology, and clinical presentation of the disease as well as the diagnostic uncertainty that exists in the critical care setting. Diagnostic approaches for deep venous thrombosis and pulmonary embolism are considered, including clinical prediction rules, D-dimer, contrast venography, duplex ultrasonography, computed tomographic angiography and venography, magnetic resonance imaging, ventilation–perfusion scanning, chest radiograph, arterial blood gases, electrocardiography, and echocardiography.

Performance of five D-dimer assays for the exclusion of symptomatic distal leg vein thrombosis

The diagnostic value of D-dimer (DD) in the exclusion of proximal deep-vein thrombosis (DVT) is well-established but is less well-known in the exclusion of distal (infrapopliteal) DVT. Therefore, we evaluated the diagnostic abilities of five DD assays (Vidas-DD, Liatest-DD, HemosIL-DD, HemosIL-DDHS, Innovance-DD) for excluding symptomatic proximal and distal leg DVT. A total of 243 outpatients whose symptoms were suggestive of DVT received complete compression ultrasonography (cCUS) of the symptomatic leg(s). The clinical probability of DVT (PTP) was assessed by Wells score. Thirty-eight proximal and 31 distal DVTs (17 tibial/fibular DVTs, 14 muscle DVTs) were diagnosed by cCUS. Although all assays showed high sensitivity for proximal DVT (range 97-100%), the sensitivity was poor for distal DVT (range 78-93%). None of the assays were individually able to rule out all DVTs as a stand-alone test (negative predictive value [NPV] 91-96%). However, a negative DD test result combined with a low PTP exhibited a NPV of 100% for all DVTs (including proximal, tibial/fibular, and muscle DVTs) with the HemosIL-DDHS and Innovance-DD. All proximal and tibial/fibular DVTs, but not all muscle DVTs, could be ruled out with this strategy using the Liatest-DD and Vidas-DD. The HemosIL-DD could not exclude distal leg DVT, even in combination with a low PTP. The combination of a negative DD with a low PTP showed a specificity of 32-35% for all DVTs. In conclusion, our study shows that when used in conjunction with a low PTP some DD assays are useful tools for the exclusion of distal leg DVT.

Relationship between disease severity and D-dimer levels measured with two different methods in pulmonary embolism patients

Pulmonary embolism (PE) is diagnosed with increasing frequency nowadays due to advances in the diagnostic methods and the increased awareness of the disease. There is a tendency to use non invasive diagnostic methods for all diseases. D-dimer is a fibrin degradation product. We aimed to detect the relationship between disease severity and the D-dimer levels measured with two different methods. We compared D-dimer levels in cases of massive vs. non-massive PE. A total of 89 patients who were diagnosed between 2006 and 2008 were included in the study. Group 1 included patients whose D-dimer levels were measured with the immunoturbidimetric polyclonal antibody method (D-dimerPLUS^®), while Group 2 patients made use of the immunoturbidimetric monoclonal antibody method (InnovanceD-DIMER^®). In each group, the D-dimer levels of those with massive and non-massive PE were compared, using the Mann Whitney U test. The mean age of Group 1 (25 F/26 M) was 56.0 ± 17.9 years, and that of Group 2 (22 F/16 M) was 52.9 ± 17.9 years. There was no statistical difference in gender and mean age between the two groups (p > 0.05). In Group 1, the mean D-dimer level of massive cases (n = 7) was 1444.9 ± 657.9 μg/L and that of nonmassive PE (n = 34) was 1304.7 ± 350.5 μg/L (p > 0.05). In Group 2, the mean D-dimer level of massive cases (n = 6) was 9.7 ± 2.2 mg/L and that of non-massive PE (n = 32) was 5.9 ± 1.3 mg/L (p < 0.05). The mean D-dimer levels of massive cases as measured with the immunoturbidimetric monoclonal antibody method were significantly higher. Pulmonary embolism patients whose D-dimer levels are higher (especially higher than 6.6 mg/L) should be considered as possibly having massive embolism. Diagnostic procedures and management can be planned according to this finding.

D-dimers and efficacy of clinical risk estimation algorithms: sensitivity in evaluation of acute pulmonary embolism

OBJECTIVE

The goal of this study was to test the efficacy of clinical risk algorithms and a quantitative immunoturbidimetric D-dimer assay in the evaluation of patients undergoing pulmonary CT angiography for suspected acute pulmonary embolism.

SUBJECTS AND METHODS

From April 1, 2007, to March 31, 2008, emergency department evaluations for clinically suspected pulmonary embolism were performed with the revised Geneva score, a quantitative D-dimer assay, and pulmonary CT angiography.

RESULTS

Evaluations for pulmonary embolism were performed for 745 consecutively registered patients, 627 of whom were included in the study. The other 118 patients were excluded because a d-dimer assay was not performed. According to the revised Geneva score, 281 patients had low clinical probability of having pulmonary embolism; 330, intermediate probability; and 16, high probability. CT angiography showed that 28 patients had pulmonary embolism (six in the low-probability group, 17 in the intermediate-probability group, and five in the high-probability group). The sensitivity, negative predictive value, and specificity of the D-dimer assay were 100%, 100%, and 25% (low-clinical-probability group); 100%, 100%, and 33% (intermediate-probability group); and 80%, 80%, and 37% (high-probability group).

CONCLUSION

The data appear to support the use of a quantitative D-dimer assay as a first-line test in evaluation for pulmonary embolism when the clinical probability of the presence of pulmonary embolism is low or intermediate. The sensitivity and negative predictive value were 100% for these cases. More than 26% of CT angiographic examinations might have been avoided if the D-dimer assay had been used as a first-line test in the care of patients at low or intermediate risk. Because of the small sample size, the D-dimer assay is not recommended as a first-line test in the evaluation of patients at high risk.

D-dimer identifies stages in the progression of diabetes mellitus from family history of diabetes to cardiovascular complications

AIM

The aim of the study was to ascertain whether there is variation in the fibrinolytic/coagulation component of diabetes associated with disease progression to macrovascular complications and whether D-dimer can discriminate such variation.

METHODS

A total of 343 participants were selected based on clinical status and divided into 7 groups: control, family history of diabetes, pre-diabetes with/without CVD, diabetes with/without CVD and CVD only. Plasma D-dimer was tested. Statistical analysis was performed on log normalised data by ANOVA, Fisher's LSD post hoc test. After the initial analysis, data were classified and re-analysed by quartiles, interquartile range and 95(th) percentile.

RESULTS

An overall significant difference between groups (p<0.002) and a steady rise in D-dimer levels that became increasingly higher than control as the disease progressed from pre-diabetes to cardiovascular complications was observed. A statistically significant difference was observed between control versus diabetes (p<0.0005). Analysis of data by quartiles and percentiles gave qualitatively similar results, but a greater significant difference between control versus pre-diabetes at 3rd quartile and interquartile range (p<0.014).

CONCLUSION

We report changes in D-dimer levels that may indicate diabetes disease progression to macrovascular complications. Using D-dimer in conjunction with other biomarkers to identify stages of disease progression, commencing from pre-diabetes and continuing to development of asymptomatic and clinical cardiovascular disease in diabetes mellitus, is worthy of consideration.

The performance of quantitative D-dimer assays in laboratory routine

Assessment of D-dimer in plasma is routinely used for the exclusion of venous thrombosis and the monitoring of hypercoagulability. Little information is available about the performance of D-dimer assays in clinical laboratories examined by external quality assessment schemes. We obtained results from 423 laboratories measuring plasma pools from patients with elevated D-dimer levels mixed with human normal plasma. The results from five samples were reported containing D-dimer from the lower normal range up to a 20-fold increased level. In addition, information about the assignment of a cut-off point and the medical need to apply these assays was obtained by standardized questionnaire. Participants reported results and additional information from 20 different assays. Lack of standardization regarding the calibration concepts obstructs comparability of results. Results in one sample varied up to 20-fold between the assays applied. In addition, a high variability was reported around the cut-off values introduced for the exclusion of venous thrombosis and pulmonary embolism. As a consequence, generally accepted cut-off values cannot be established. For cut-off assignment, 62% of participants used the kit insert but also 14% used local validation. In conclusion, standardization or at least harmonization of D-dimer assays is necessary to ensure comparability of D-dimer plasma levels measured in clinical routine.

Variation in the diagnostic performance of D-dimer for suspected deep vein thrombosis

BACKGROUND

Numerous studies have evaluated the accuracy of D-dimer in diagnosing suspected deep vein thrombosis (DVT), but results are conflicting.

AIM

To overview estimates of the diagnostic accuracy of D-dimer and identify causes of variation.

DESIGN

Systematic review, meta-analysis and meta-regression.

METHODS

We searched Medline, EMBASE, CINAHL, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Controlled Trials Register, Database of Reviews of Effectiveness, the ACP Journal Club, citation lists, and contacted manufacturers. We selected studies that compared D-dimer to a reference standard in patients with suspected DVT. Data were analysed by random effects meta-analysis and meta-regression.

RESULTS

We included 97 studies reporting 198 assays in 99 different patient groups. Overall estimated sensitivity and specificity of D-dimer were 90.5% and 54.7%, but both estimates were subject to significant heterogeneity (p < 0.001). Meta-regression identified that some heterogeneity was explained by study setting, exclusion criteria, whether recruitment was consecutive or the study prospective, whether D-dimer and the reference standard were measured blind, and whether the D-dimer threshold was determined a priori. Sensitivity and specificity also varied between ELISA (94% and 45% respectively), latex (89% and 55%) and whole blood agglutination assays (87% and 68%). Sensitivity was higher for proximal than distal DVT. Specificity was dependent upon whether clinical probability of DVT was high (specificity 51%), intermediate (67%) or low (78%).

DISCUSSION

D-dimer has good sensitivity, but poor specificity, for DVT. Estimates are subject to substantial heterogeneity from various sources. D-dimer specificity appears to be strongly dependent upon the pre-test clinical probability of DVT.

An evaluation of rapid D-dimer assays for the exclusion of deep vein thrombosis

We evaluated the performance of eight d-assays for the exclusion of deep vein thrombosis (DVT); Biopool AutoDimer, Biopool MiniQuant, bioMèrieux MDA D-Dimer, VIDAS, Dade Behring D-Dimer Plus, Trinity Biotech AMAX, NycoCard D-dimer and IL Test D-Dimer. The assays were evaluated both as stand-alone tests, and in combination with pretest probability (PTP). D-dimer assays and PTP assessment were performed on 410 patients presenting to the emergency department with suspected acute DVT. DVT was diagnosed in 76 of 410 patients (18.5%) by compression ultrasound or other imaging techniques, as required. Receiver operator characteristics analysis established optimum cut-off values and these were compared with manufacturer's cut-off values where provided. As stand-alone tests, the assays varied immensely regarding cut-off value, negative predictive value (NPV 93-100%) and specificity (0-67%). At least one patient with confirmed DVT had a low d-dimer level by each method: to achieve 100% sensitivity it would be necessary to reduce cut-off values to levels below clinical usefulness. When low d-dimer was used in combination with PTP, six of eight methods achieved > or =98% NPV, with a diagnosis of DVT excluded in 16-44% of patients without the requirement for diagnostic imaging. The highly variable diagnostic performance of these d-dimer assays means that some assays are unsuitable for certain diagnostic strategies. However, our data suggest that the combination of sensitive D-dimer assays with an assessment of PTP may be used to exclude a diagnosis of DVT.

Exclusion of venous thromboembolism: evaluation of D-Dimer PLUS for the quantitative determination of D-dimer

The objective of this study was to evaluate if D-Dimer PLUS (Dade Behring, USA), a rapid fully automated assay, could be used as an initial screening test in the diagnosis of venous thromboembolism (VTE). Samples from 274 consecutive symptomatic patients with suspected pulmonary embolism (n=229; 79% outpatients, 21% inpatients), deep venous thrombosis (n=37; 84% outpatients, 16% inpatients) or suspected for both complications (n=8) were tested with this D-dimer assay with a Sysmex CA-1500 Coagulation Analyzer. Clinical probability for pulmonary embolism (PE) or deep venous thrombosis (DVT) was staged according to a pretest risk score proposed by Wells. Final diagnosis of PE and/or DVT was established by spiral-computed tomography of the pulmonary arteries or compression ultrasonography, respectively. PE was diagnosed in 13.5% of the patients, whereas DVT was confirmed in 17.7% of the patients. The optimal cut-off value for exclusion of venous thromboembolism was 130 mug/l, and sensitivity, specificity and negative predictive value (NPV) were 95.0% (95% CI: 92.4-97.6), 30.4% (95% CI: 25.0-35.8) and 97.2% (95% CI: 95.2-99.2), respectively. In fact, two patient with PE were missed using D-Dimer PLUS; both cases were outpatients. In conclusion, this assay appears to be safe when implemented in an algorithm based on clinical assessment, D-dimer concentration, and radiological diagnostic techniques to stratify the risk for PE or DVT. However, higher sensitivities and negative predictive values were claimed in the scarce published reports for the D-Dimer PLUS assay than found in this study.